Chronic Glutathione Depletion Confers Protection against Alcohol-induced Steatosis: Implication for Redox Activation of AMP-activated Protein Kinase Pathway.

Ying Chen,Akiko Matsumoto,Hongbin Dong,Srujana Golla,Soumen K Manna,Frank J Gonzalez,Byoung-Joon Song,Surendra Singh,Vasilis Vasiliou,David C Thompson,Robert C Murphy,Mohamed A Abdelmegeed

doi:10.1038/srep29743

Abstract

The pathogenesis of alcoholic liver disease (ALD) is not well established. However, oxidative stress and associated decreases in levels of glutathione (GSH) are known to play a central role in ALD. The present study examines the effect of GSH deficiency on alcohol-induced liver steatosis in Gclm knockout (KO) mice that constitutively have ≈15% normal hepatic levels of GSH. Following chronic (6 week) feeding with an ethanol-containing liquid diet, the Gclm KO mice were unexpectedly found to be protected against steatosis despite showing increased oxidative stress (as reflected in elevated levels of CYP2E1 and protein carbonyls). Gclm KO mice also exhibit constitutive activation of liver AMP-activated protein kinase (AMPK) pathway and nuclear factor-erythroid 2–related factor 2 target genes, and show enhanced ethanol clearance, altered hepatic lipid profiles in favor of increased levels of polyunsaturated fatty acids and concordant changes in expression of genes associated with lipogenesis and fatty acid oxidation. In summary, our data implicate a novel mechanism protecting against liver steatosis via an oxidative stress adaptive response that activates the AMPK pathway. We propose redox activation of the AMPK may represent a new therapeutic strategy for preventing ALD.

Highlights

The pathogenesis of alcoholic liver disease (ALD) is not well established
Compared with EtOHfed WT mice, KO mice were less susceptible to EtOH-induced deleterious effects, including body weight loss, liver weight gain and hepatocyte damage (Table 1)
It is worth noting that histological examination of the liver revealed no significant liver inflammation in either WT or KO mice (Fig. 1), which is further supported by unaltered mRNA levels of inflammatory genes TNFα, IL-6 and IL-1β(supplementary Fig. 1)

Summary

Introduction

The pathogenesis of alcoholic liver disease (ALD) is not well established. oxidative stress and associated decreases in levels of glutathione (GSH) are known to play a central role in ALD. The present study examines the effect of GSH deficiency on alcohol-induced liver steatosis in Gclm knockout (KO) mice that constitutively have ≈15% normal hepatic levels of GSH. Manifestations of hepatic oxidative damage include dysregulation of lipid metabolism (leading to steatosis), hepatocyte degeneration and death, and activated immune response (leading to inflammation and fibrosis/cirrhosis). These are all features of ALD depending on the disease stage[5]. Treatment of newborn rats with L-buthionine sulfoximine (BSO), an irreversible inhibitor of GCLC, leads to hepatic abnormalities including mitochondrial dysfunction[10] These studies underscore the essential role of GSH in normal functioning of the liver. Following 6 wk of ethanol administration, GCLM knockout mice were resistant to alcohol-induced steatosis and exhibited beneficial metabolic and stress responses to chronic ethanol consumption

Methods

Results

Conclusion